Effect of Thermal Aging on Electrical Properties of Low Density Polyethylene

Wang, Can,Xie, Yaoheng,Pan, Hua,Wang, Youyuan The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

The thermal degradation of low density polyethylene (LDPE) will accelerate the production of carbonyl groups (C=O), which can act as the induced dipoles under high voltage. In this paper, we researched the dielectric properties and space charge behavior of LDPE after thermal aging, which can help us to understand the correlation between carbonyl groups (C=O) and electrical properties of LDPE. The spectra results show that LDPE exhibit obvious thermooxidative reactions when the aging time is 35 days and the productions mainly contain carboxylic acid, carboxylic eater and carboxylic anhydride, whose amount increase with the increasing of aging time. The dielectric properties show that the real permittivity of LDPE is inversely proportional to temperature before aging and subsequently become proportional to temperature after thermal aging. Furthermore, both the real and imaginary permittivity increase sharply with the increasing of aging time. The fitting results of imaginary permittivity show that DC conductivity become more sensitive about temperature after thermal aging. On this basis, the active energies of materials calculated from DC conductivity increase first and then decrease with the increasing of aging time. In addition, the space charge results show that the heterocharges accumulated near electrodes in LDPE change to the homocharges after thermal aging and the mean volume charge density increase with the increasing of aging time. It is considered that the overlaps caused by electrical potential area is the main reason for the increase of DC conductivity.

Effect of Thermal Aging on Electrical Properties of Low Density Polyethylene

Can Wang,Yaoheng Xie,Hua Pan,Youyuan Wang 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

The thermal degradation of low density polyethylene (LDPE) will accelerate the production of carbonyl groups (C=O), which can act as the induced dipoles under high voltage. In this paper, we researched the dielectric properties and space charge behavior of LDPE after thermal aging, which can help us to understand the correlation between carbonyl groups (C=O) and electrical properties of LDPE. The spectra results show that LDPE exhibit obvious thermooxidative reactions when the aging time is 35 days and the productions mainly contain carboxylic acid, carboxylic eater and carboxylic anhydride, whose amount increase with the increasing of aging time. The dielectric properties show that the real permittivity of LDPE is inversely proportional to temperature before aging and subsequently become proportional to temperature after thermal aging. Furthermore, both the real and imaginary permittivity increase sharply with the increasing of aging time. The fitting results of imaginary permittivity show that DC conductivity become more sensitive about temperature after thermal aging. On this basis, the active energies of materials calculated from DC conductivity increase first and then decrease with the increasing of aging time. In addition, the space charge results show that the heterocharges accumulated near electrodes in LDPE change to the homocharges after thermal aging and the mean volume charge density increase with the increasing of aging time. It is considered that the overlaps caused by electrical potential area is the main reason for the increase of DC conductivity.

Preliminary study on a 3D field permanent magnet flux switching machine - from tubular to rotary configurations

Wang, Can-Fei,Shen, Jian-Xin Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.4

A permanent magnet flux switching (PMFS) machine has a simple rotor, whilst both magnets and coils are set in the stator, resulting in easy removal of heat due to both copper loss and eddy current loss in magnets. However, the volume of magnets used in PMFS machines is usually larger than in conventional PM machines, and leakage flux does exist at the non-airgap side. To make full use of the magnets and gain higher power density, a novel 3-dimensional (3D) field PMFS machine is developed. It combines merits of the tubular linear machine, external-rotor rotary machine and axial-flux rotary machine, hence, offers high power density and peak torque capability, as well as efficient utility of magnets owing to the unique configuration of triple airgap fields.

Field Study on Evaluation of Axial Stiffness and Load Sharing Behavior of Micropiles

Wang, Cheng Can,Kim, Seok Jung,Han, Jin Tae 대한토목학회 2020 대한토목학회 학술대회 Vol.2020 No.10

The Effect of Hygrothermal Aging on the Properties of Epoxy Resin

Wang, Youyuan,Liu, Yu,Xiao, Kun,Wang, Can,Zhang, Zhanxi The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

Because of excellent electrical properties, epoxy resin is widely used in packaging and casting power equipment. Moisture and temperature in the environment are inclined to seriously affect the insulation tolerance of epoxy resin. This work focuses on the aging characteristics of epoxy resin in hygrothermal environment. Scanning electron microscopy images show that there are micro-crack, micro-slit and holes inside aged samples. The moisture absorption process undergoes three equilibrium stages and it does not follow the Fick's second law. Observing the change of hydrogen bonds in the infrared spectra of the dried samples, it is found that chemically moisture absorption immerges when the physical moisture absorption entered the third equilibrium stage. By Debye equation to fit the imaginary part of the dielectric constant, it is concluded that the uniformity of water molecule has a great influence on the electrical conductivity loss. Furthermore, the polarization loss can be more easily affected by water molecules than small free molecules. After the aged samples being dried, their real and imaginary part of the dielectric constant descend, but their original electrical properties cannot completely restored. After chemical moisture absorption appears inside the material, the residual space charges increase significantly and the charge dissipation rate slow down obviously.

Properties of Fe-based Cr3C2 Coatings Produced with a High-Velocity Arc-Spraying Process

Can-Ming Wang,Hong-Fei Sun,Zhiyan Qu,Qiang Song 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.3

Fe-based Cr3C2 coatings were sprayed with a high-velocity spraying process. The main phases of the coatings were α-Fe, (Fe, Cr)23C6, (Fe, Cr)7C3, FeCr2O4, Cr3C2 and a small amount of Fe3Si. The abrasive wear performances of the coatings were tested by using a rubber wheel abrasive tester. The wear mechanisms of the coatings were mainly plastic cutting and brittle fracture of some ceramic phases. At 650℃ the erosion rate of the coatings had a peak value at 40℃ impingement angles. The coatings exhibited excellent erosion resistance at high temperatures and were suitable for use in circulating fluid-bed boilers. Fe-based Cr3C2 coatings were sprayed with a high-velocity spraying process. The main phases of the coatings were α-Fe, (Fe, Cr)23C6, (Fe, Cr)7C3, FeCr2O4, Cr3C2 and a small amount of Fe3Si. The abrasive wear performances of the coatings were tested by using a rubber wheel abrasive tester. The wear mechanisms of the coatings were mainly plastic cutting and brittle fracture of some ceramic phases. At 650℃ the erosion rate of the coatings had a peak value at 40℃ impingement angles. The coatings exhibited excellent erosion resistance at high temperatures and were suitable for use in circulating fluid-bed boilers.

Protective enzymes and genes related to the JA pathway are involved in the response to root-knot nematodes at high soil temperatures in tomatoes carrying Mi-1

Canli Hu,Wenchao Zhao,Jingwei Fan,Zilong Li,Rui Yang,Fukuan Zhao,JianLi Wang,Shaohui Wang 한국원예학회 2015 Horticulture, Environment, and Biotechnology Vol.56 No.4

Root-knot nematodes (RKNs; Meloidogyne spp.) are obligate endoparasites that infect a large number of crop plants and cause severe yield losses. Tomato cultivars carrying the Mi-1 gene conferring root-knot nematode resistance have been widely used, but this gene loses its effectiveness at soil temperatures above 28°C. In this study, the mechanism of the loss of resistance to RKNs at high soil temperatures was examined using LA0655 (Solanum lycopersicum cv. Anahu), which contains the Mi-1 gene. It was found that high soil temperatures delayed the expression of the Mi-1 gene and reduced the activities of superoxide dismutase, peroxidase, chitinase, and β-1,3-glucanase. Although genes in the jasmonic acid (JA) pathway exhibited an obvious response at high soil temperatures, this response could not prevent the invasion of RKNs; indeed, at 30 days after inoculation with RKNs, the plants produced large numbers of root knots and egg masses at a soil temperature of 32°C.

Variations in bacterial and fungal communities through soil depth profiles in a Betula albosinensis forest

Can Du,Zengchao Geng,Qiang Wang,Tongtong Zhang,Wenxiang He,Lin Hou,Yueling Wang 한국미생물학회 2017 The journal of microbiology Vol.55 No.9

Microbial communities in subsurface soil are specialized for their environment, which is distinct from that of the surface communities. However, little is known about the microbial communities (bacteria and fungi) that exist in the deeper soil horizons. Vertical changes in microbial alpha-diversity (Chao1 and Shannon indices) and community composition were investigated at four soil depths (0–10, 10–20, 20–40, and 40–60 cm) in a natural secondary forest of Betula albosinensis by high-throughput sequencing of the 16S and internal transcribed spacer rDNA regions. The numbers of operational taxonomic units (OTUs), and the Chao1 and Shannon indices decreased in the deeper soil layers. Each soil layer contained both mutual and specific OTUs. In the 40–60 cm soil layer, 175 and 235 specific bacterial and fungal OTUs were identified, respectively. Acidobacteria was the most dominant bacterial group in all four soil layers, but reached its maximum at 40–60 cm (62.88%). In particular, the 40–60 cm soil layer typically showed the highest abundance of the fungal genus Inocybe (47.46%). The Chao1 and Shannon indices were significantly correlated with the soil organic carbon content. Redundancy analysis indicated that the bacterial communities were closely correlated with soil organic carbon content (P = 0.001). Collectively, these results indicate that soil nutrients alter the microbial diversity and relative abundance and affect the microbial composition.

Lentivirus Mediated GOLPH3 shRNA Inhibits Growth and Metastasis of Esophageal Squamous Cancer

Wang, Qiang,Wang, Xian,Zhang, Can-Bin Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.9

Aim: To investigate the role of Golgi phosphoprotein 3 (GOLPH3) in tumour growth and metastasis of esophageal squamous cancer. Methods: A lentiviral shRNA-vector was utilized to stably knockdown GOLPH3 in Eca-109 esophageal squamous cancer cells. mRNA transcription and protein expression of GOLPH3 were examined by real-time quantitative PCR and Western blotting, respectively. Cell proliferation activity was assessed by MTT assay and invasion and migration potentials by matrigel invasion and transwell motility assays. Results: Stable knockdown in the GOLPH3 cell line was established. PD-A gene expression was significantly suppressed by lentivirus-mediated RNAi, which resulted in reducing the capacity for cell proliferation, migration, invasion and adhesion in vitro. In vivo, GOLPH3 depletion resulted in inhibition of tumour growth, with stable decrease in the expression of GOLPH3 in tumor xenografts. Conclusions: Our findings suggest that lentivirus mediated silencing of the GOLPH3 gene has a significant anti-tumour effect on esophageal squamous cancer in vitro and in vivo. In addition, the results indicate that GOLPH3 might be an effective molecular target for gene therapy in esophageal squamous cancer.

Experimental Analysis of Wheel Mobility performance for Planetary Rovers on Lunar Soil Simulant

Wang, Cheng Can(왕성찬),Han, Jin Tae(한진태),Lee, Joon Yong(이준용) 대한토목학회 2016 대한토목학회 학술대회 Vol.2016 No.10